This application claims benefit of priority under 35USC xc2xa7119 to Japanese Patent Application No. 2000-70265, filed on Mar. 14, 2000, the contents of which are incorporated by reference herein.
1. Field of the Invention
The present invention relates generally to a magnetic head and a magnetic recording and reproducing system. More specifically, the invention relates to a recording and reproducing magnetic head capable of carrying out an effective recording and reproducing with low noises in a vertical magnetic recording system, and a recording and reproducing system using the same.
2. Description of Related Art
In recent years, magnetic recording systems, such as hard disk drives (HDDs), are rapidly miniaturized and densified, and expected to be further densified in future. In order to increase the density in magnetic recording, it is required to narrow the recording track width to enhance the recording track density, and it is required to enhance the recording density in longitudinal directions of the recording track, i.e., the xe2x80x9ctrack recording densityxe2x80x9d.
However, in a so-called inplane recording system (longitudinal recording system), as the recording density increases, there are remarkably caused problems in that the diamagnetic field increases, the regenerative output decreases, and stable recording operations can not be carried out. As a system for eliminating these problems, the vertical recording system is proposed. The vertical recording system is designed to magnetize in directions substantially perpendicular to the surface of a recording medium to record signals, and has advantages in that even if the recording density increases, the influence of the diamagnetic field is small and the lowering of the regenerative output is suppressed as compared with the inplane recording system.
In either of the inplane recording system or the vertical recording system, an inductive head is conventionally used for reproducing signals which have been recorded on medium. However, the anisotropic magnetoresistive (AMR) head, which uses the magnetoresistance effect and which has a high regenerative sensitivity, is developed to be used as a shielded reproducing head so that a sufficient regenerative signal output can be obtained even if the recording track width becomes narrower and the magnitude of recorded magnetization decreases with the increase of density. In recent years, the spin-valve-type GMR head utilizing the giant magnetoresistance effect is used. Moreover, a magnetic head using the tunneling magnetoresistance effect (TMR), which is expected to have a higher regenerative sensitivity, is developed and studied for practical use. Thus, magnetic heads having a high regenerative sensitivity have been developed. By using these magnetic heads, a recording signal begins to be able to be recorded even if it has a very small recording bit size.
By the way, in order to enhance the track recording density which is the density in longitudinal directions of a recording track, it is required to narrow the gap of a magnetic head. However, in the above-described conventional magnetic heads using the magnetoresistance effect, a magnetoresistance effect element is provided in a head gap. Even in the case of the AMR head or the spin-valve GMR head, the thickness of the magnetoresistance effect element must be about 30 nm, and 100 nm between shields in view of insulation from shields. For that reason, in the conventional type of magnetic heads, the thickness of the magnetoresistance effect element capable of narrowing the head gap is limited to about 100 nm. Therefore, there is a severe limit to the enhancement of track recording density.
Accordingly, it is desired to provide a magnetoresistance effect type magnetic head of a type capable of sufficiently narrowing a head gap without providing a magnetoresistance effect element in the gap of a magnetic head, for incorporating a magnetic flux from recorded magnetization by means of a head gap portion to guide the magnetic flux into the magnetic head by means of a magnetic yoke to transmit a magnetoresistance effect element which is arranged in the rear portion of the magnetic head, i.e., a magnetoresistance effect type magnetic head of xe2x80x9cyoke typexe2x80x9d. Since this yoke type magnetic head can sufficiently decrease the head gap, it is expected that the yoke type magnetic head can improve the resolution in reproduction and can correspond to a high track recording density. With respect to the track density, although a conventional type magnetic head defines a regenerative track width by intervals of leads which are provided for supplying a sense current to both ends of a magnetoresistance effect element, the yoke type magnetic head can define a track width by the thickness of a yoke film, so that the yoke type magnetic head can more easily narrow the track width than the conventional type magnetic head. From these facts, it is expected that the yoke type magnetic head can particularly sufficiently adapt to the enhancement of recording density in future.
On the other hand, it is also required to provide a recording head for writing in order to construct a magnetic head for HDD. Although there is the same advantage in a recording head in the case of a planar type head capable of a track width by a thickness, it is very difficult to provide this recording head with a coil for generating a magnetomotive force. Although it is required to provide the coil so as to pass above and below a magnetic pole, the process for producing the coil is not only complicated, but it is also not easy to increase the turn number of the coil. In order to eliminate these problems, the coil may be prepared in the plane of a substrate. However, in this case, a reproducing head must be prepared on the side of the substrate, so that the process is more complicated.
Particularly in the case of the vertical recording system, there is proposed a recording medium disk having a double-layer film structure wherein a xe2x80x9cmagnetically soft backing layerxe2x80x9d is provided below a magnetizing recording layer in order to enhance recording and reproducing efficiencies. Using such a medium, the demagnetization field at the tip of the magnetic head can be reduced by the magnetic interaction between the magnetic head and the magnetically soft backing layer. Therefore, a greater generated magnetic field can be obtained during a recording operation, and a greater regenerative signal can be obtained during a reproducing operation.
However, in such a vertical magnetic recording system using the double-layer recording medium having the magnetically soft backing layer, there is a problem in that noises are generated due to the magnetically soft backing layer. These noises are generated by the variation in magnetized state of the magnetically soft backing layer. Typical noises are Barkhausen noises caused by the movement of magnetic domain walls.
Since a relatively strong magnetic flux passes through the backing layer during a recording operation, the magnetized state at that place is disturbed to cause the generation of noises during a reproducing operation. In particular, when the recording density is high and when a sensitive magnetoresistance effect element is used as a reproducing head, the recording bit size is small, so that the quantity of magnetic fluxes generated by the recording layer is small. Therefore, there are problems in that the influence of noises increases, so that S/N decreases during a reproducing operation.
By the residual magnetization of a recording pole, a magnetic circuit is always formed by the main pole of the recording head, the magnetically soft backing layer and a return yoke although it has a smaller magnetic field than that during a recording operation. During a recording operation, there is no problem since a stronger magnetic field is generated. However, during a reproducing operation, the source of magnetomotive force only has recording bits of the recording layer. In particular, as the recording density increases, the bit size decreases, so that the generated magnetic fluxes decrease. Therefore, the influence of residual magnetization of the recording pole becomes remarkable, so that the reproducing efficiency is caused to decrease.
It is therefore an object of the present invention to eliminate the aforementioned problems and to provide a magnetic head for vertical magnetic recording, which can suppress noises due to a magnetically soft layer and which can improve the lowering of efficiency, and a magnetic recording and reproducing system using the same.
In order to accomplish the aforementioned and other objects, there is provided a magnetic head comprising: a recording head comprising a first main pole and a first return yoke, the first main pole having a first medium facing portion, the first return yoke having a second medium facing portion, the first and second medium facing portions are disposed with first magnetic gap therebetween, a reproducing head comprising a second main pole and a second return yoke, the second main pole having a third medium facing portion, the second return yoke having a fourth medium facing portion, the third and fourth medium facing portions are disposed with second magnetic gap therebetween, first angle xcex81 between first and second straight lines being smaller than second angle xcex82 between the first straight line and third straight line, the first straight line connecting centers of medium facing surfaces of the first medium facing portion and the second medium facing portion, the second straight line connecting opposing corners of medium facing surfaces of the first medium facing portion and the second medium facing portion, and the third straight line connecting centers of medium facing surfaces of the third medium facing portion and the fourth medium facing portion.
The xe2x80x9cmain polexe2x80x9d of the magnetic head is a portion for recording on a medium in a predetermined track width using magnetic fluxes which are generated by passing current through a coil. The xe2x80x9creturn yokexe2x80x9d of the recording head is provided for forming a magnetic circuit, and usually has a wider area on the medium facing surface than the main pole.
The xe2x80x9cmain polexe2x80x9d and xe2x80x9creturn yokexe2x80x9d of the reproducing head are basically the same as those of the recording head. However, the xe2x80x9cmain polexe2x80x9d and the xe2x80x9creturn yokexe2x80x9d often substantially have the same shape, so that they are often expressed by xe2x80x9cyokesxe2x80x9d. In such cases, for convenience, one of them is interpreted as the main pole, and the other is interpreted as the return yoke, so that the above described definition is used.
When the reproducing head is a shielded reproducing head, a magnetoresistance effect element itself corresponds to the main pole, and a shield corresponds to the return yoke.
If a magnetic head according to the present invention is used for recording on a vertical magnetic recording medium comprising a magnetically soft backing layer and a vertical recording layer, magnetic fluxes flow through a range of xc2x1xcex81 with respect to the line drawn between the centers of the main pole and return yoke of the recording head of the magnetically soft backing layer. Then, this place is read out by the reproducing head, the direction of magnetic fluxes flowing through the magnetically soft backing layer during the reproducing operation is not coincident with the direction of magnetic fluxes flowing through the magnetically soft backing layer during the recording operation.
As a result, it is possible to eliminate problems in that Barkhausen noises are generated and the reproducing efficiency is lowered when both directions are coincident with each other.
If the magnetic head according to the present invention is constructed so that the xcex82 is substantially 90xc2x0, the magnetoresistance effect element serving as an important portion of the reproducing head, and the large complicated-shaped recording head exciting coil can be formed on the same plane, specifically on the plane of the substrate. Therefore, the producing process can not only be simplified, but it is also possible to further suppress Barkhausen noises since magnetic fluxes flow in pseudo directions, in which magnetization is difficult, when a reproducing operation is carried out so that magnetic fluxes flow in directions perpendicular to the direction of magnetic fluxes having flowed during a recording operation.
If the magnetic head is constructed so that the line drawn between the center of the main pole of the reproducing head and the center of the return yoke of the reproducing head is substantially parallel to the longitudinal directions of a recording track which is formed on a recording medium, the efficiency during a reproducing operation can be enhanced for the following reasons.
That is, during a recording operation, the bit size is determined by the shape of the main pole, the rotating speed of the medium disk and the frequency of writing current. The recording efficiency does not so depend on the directions of the line, which is drawn between the center of the main pole and the center of the return yoke, with respect to the track directions, and the directions of the line may be the directions of the track width. This can be accomplished if the sufficient quantity of magnetic fluxes can be supplied from the coil and the shape of the main pole is optimized. On the other hand, during a reproducing operation, resolution can be defined by determining the shape in accordance with the recorded bit size. However, since the track width is generally greater than the bit length, the size can be minimum when the line drawn between the center of the main pole and the center of the return yoke extends in the longitudinal directions of the track, i.e., the directions of the bit length.
As the recording density increases, the bit size decreases, and the quantity of generated magnetic fluxes decreases. Therefore, in order to increase the reproducing efficiency, it is desired that the distance between the main pole and the return yoke is as small as possible. If the line drawn between the center of the main pole and the center of the return yoke extends in the longitudinal directions of the track, both of the definition of resolution and the increase of the efficiency can be achieved.
In addition, if the main pole of the recording head also serves as the main pole of the reproducing head, it is possible to avoid the shift of the position of the recording track from the position of the reproducing track, so that it is possible to provide a very advantageous structure for increasing the recording density. If the main poles of the recording head and reproducing head are separately arranged, the shift between the track positions of the recording head and reproducing head if the skew angle varies. In order to avoid this, the recording track width is set to be wider than the reproducing track width so that there is no problem even if the skew angle varies. In that case, in order to increase the recording density, there is a problem in that the track width must be finally widened.
Therefore, if the recording main pole is the same as the reproducing main pole, the track position is not shifted even if the skew angle varies, so that it is not required to widen the recording track. As a result, since the minimum track width can be used, the track density increases, so that the recording density is improved.
The magnetic recording and reproducing system of the vertical magnetic recording system according to the present invention has any one of the above described magnetic heads according to the present invention. In particular, if the system is combined with the vertical double-layer medium using the magnetically soft backing layer, it is possible to realize excellent recording/reproducing characteristics.
This magnetic recording and reproducing system comprises: a slider on which any one of the above described magnetic heads is formed; a suspension for supporting the slider and for suitably holding the distance between a medium and the slider; a driving part for positioning the head; a medium disk; and a driving part for rotating the medium disk.
In a recording operation using this magnetic recording and/or reproducing system, current is passed through the coil of the recording head to generate magnetic fluxes which are focused on the main pole to write on the medium disk. At this time, the magnetic fluxes passing through the recording layer pass through the magnetically soft backing layer to return to the return yoke to form a magnetic circuit, so that the recording efficiency is improved. In a reproducing operation, magnetic fluxes from the recording bit, which has been recorded, are sucked into the main pole of the reproducing head to pass through the magnetoresistance effect element serving as a sensor, the return yoke and the backing layer to return to the recording bit to form a magnetic circuit, so that it is possible to efficiently carry out the reproducing operation. A regenerative signal is detected as the variation in resistance when a magnetic flux passes through the magnetoresistance effect element.
Moreover, if the stacked film comprising the antiferromagnetic film and the magnetically soft film is used as the magnetically soft backing layer, it is possible to provide a more excellent magnetic recording and/or reproducing system. If this is combined with the magnetic head according to the present invention, the direction of magnetic fluxes flowing through the magnetically soft backing layer during the recording operation is different from that during the reproducing operation. If the magnetically soft backing has a magnetic anisotropy, the magnetic permeability varies in accordance with direction, so that the efficiency drops during any one of recording and reproducing operations. If a magnetic domain wall is produced on the magnetically soft backing layer, noises are generated when the magnetic head pass through the magnetic domain wall. Also, if the magnetic domain wall of the magnetically soft backing layer is moved by a disturbance magnetic field generated from a head positioning or disk rotating motor, noises are generated. Therefore, it is desired to provide a film which is a magnetically isotropic film wherein no magnetic domain wall is produced on the magnetically soft backing layer. For that reason, if the stacked film comprising the antiferromagnetic film and the magnetically soft film is used as the backing layer, the generation of magnetic domain walls can be suppressed by the switched connection between the antiferromagnetic film and the magnetically soft film, and the backing layer can be a magnetically isotropic film. It is possible to obtain a film having such characteristics by applying a rotating magnetic field during the deposition of the antiferromagnetic film and magnetically soft film or by carrying out a thermal treatment in a rotating magnetic field after the deposition. Therefore, the magnetic recording and/or reproducing system, wherein the magnetic head according to the present invention is combined with the vertical double-layer medium using an antiferromagnetic film and the magnetically soft film as the backing layer, is an excellent magnetic recording and/or reproducing system wherein the influence of noises is suppressed even if the recording density increases.